Summary
Although many Latin abbreviations once used in academic references have largely disappeared from modern publishing practices, some continue to appear in footnotes, endnotes and historical scholarship. Among the most misunderstood are “ibid.” (short for ibidem) and the “id.” family (short for idem, eadem and related forms). Because these abbreviations follow precise grammatical rules—and because incorrect usage causes confusion for editors, reviewers and readers—authors must understand exactly when, how and why to use them.
This expanded guide explains the meaning, history and correct application of “ibid.” and the “id.” group; clarifies how to manage gender and number; outlines when these abbreviations should not be used; and highlights when publishers forbid them entirely. It also discusses how to incorporate them ethically into modern scholarly referencing while avoiding misinterpretation or ambiguity.
Whether you encounter these abbreviations in historical works, are required to use them for your field, or simply want to understand their mechanics, this guide equips you with the knowledge to apply them accurately, consistently and professionally in academic manuscripts.
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Understanding “Ibid.” and “Id.” for Accurate Academic Referencing
While most Latin abbreviations once common in academic referencing have disappeared from contemporary manuscripts, a handful remain in use—particularly in the humanities, legal scholarship, archival research and historically oriented disciplines. Two categories that often puzzle researchers today are “ibid.” and the “id.” group (id., ead., eid., eaed., and occasionally their full Latin forms). Because these forms appear primarily in footnotes and endnotes rather than in-text citations, they are frequently encountered in older scholarship or in disciplines that retain traditional referencing conventions.
Yet many modern authors have never been taught their meanings or how to apply them properly. Misuse leads to confusion, editorial corrections and, in some cases, rejection or demands for revision. This expanded guide explains how to use “ibid.” and the “id.” family correctly and highlights the circumstances under which you should avoid them.
1. Why Latin Abbreviations Still Matter
Latin abbreviations were once staples of scholarly referencing, when most research was circulated in languages heavily influenced by classical education. Today, most referencing styles (e.g., APA, MLA, Chicago Author–Date, Harvard) avoid or discourage Latin abbreviations in favour of transparency and global readability.
However, several citation systems still employ them:
• Chicago humanities notes-and-bibliography,
• legal referencing (including international law),
• classical studies, medieval studies and philology,
• philosophy and theology,
• archival and primary-source annotation.
Even when your field no longer uses these forms, you may encounter them in older scholarship or archival sources. Understanding them is therefore beneficial for all researchers, especially those preparing manuscripts for publication.
2. “Ibid.” — Meaning, Function and Correct Usage
“Ibid.” is an abbreviation of the Latin word ibidem, which means “in the same place” or “in that very place.” It refers not to a book or article title specifically, but to the entire preceding citation.
2.1 When to Use “Ibid.”
Use “ibid.” only when the very next citation (the immediately following note or reference line) refers to exactly the same source as the previous one.
Examples:
1. Smith, Ecology of Birds, 55.
2. Ibid.
This means that citation 2 refers to Smith’s Ecology of Birds, page 55.
2.2 When “Ibid.” Must Be Qualified
If the source is the same but the page number (or location) is different, add the new location:
1. Smith, Ecology of Birds, 55.
2. Ibid., 61.
This indicates “the same source, but page 61.”
Important: Some style guides require a comma before the page number; others forbid it. Always check the journal’s guidelines.
2.3 When Not to Use “Ibid.”
Avoid “ibid.” when:
• there is any intervening citation,
• the preceding footnote contains multiple sources,
• the reference could be ambiguous,
• your style guide prohibits it (many do),
• your target journal prioritises clarity over tradition.
Never use “ibid.” if the identity of the source is even slightly uncertain.
3. The “Id.” Group — Understanding Gender and Number
The abbreviation id. stands for idem, meaning “the same person” (masculine). Unlike “ibid.,” which stands for an entire citation, “id.” replaces the author name only.
Because Latin is inflected for gender and number, related forms include:
• id. or idem — masculine singular, “the same man/person,”
• ead. or eadem — feminine singular, “the same woman/person,”
• eid. or eidem — masculine or mixed-gender plural, “the same people,”
• eaed. or eaedem — feminine plural, “the same women.”
3.1 When to Use “Id.” Forms
Use “id.” or one of its variants only when:
• two or more works by the same author(s) are cited consecutively,
• replacing the author’s name reduces repetition,
• your style guide permits Latin abbreviations,
And:
• you choose the correct form for the author’s gender and number.
Example (male author):
1. John Adams, Political Reform, 88.
2. Id., Republican Virtues, 41.
Example (female author):
1. Sarah Lee, Marine Ecosystems, 212.
2. Ead., Ocean Currents, 44.
Example (two male or mixed-gender authors):
1. Chen and Patel, AI in Medicine, 144.
2. Eid., Neural Interfaces, 53.
3.2 When Not to Use “Id.” Forms
Avoid these abbreviations if:
• the authorship could be unclear,
• the gender is unknown,
• the style guide forbids Latin terms,
• a corporate or institutional author is used,
• the reference style requires full repeated names.
When in doubt, write the author’s name again. Clarity is more important than brevity.
4. Common Confusions: “Ibid.” vs “Id.” vs “Op. cit.”
These Latin abbreviations are often mixed up, especially in older scholarship.
• Ibid. = the same citation as the one immediately preceding.
• Id. = the same author as the immediately preceding reference.
• Op. cit. = “in the work cited” (largely obsolete and not recommended).
Only “ibid.” refers to the same source. Only “id.” refers to the same author.
5. Font Style: Roman or Italic?
Both “ibid.” and “id.” traditionally appear in roman font, but some publishers prefer italics. Because style guides vary:
• Chicago NB = roman,
• many European humanities presses = italics,
• legal writing = roman,
• classical philology = italics optional.
Whichever style you choose, apply it consistently.
6. When Modern Journals Avoid These Abbreviations
Many contemporary journals discourage or prohibit Latin abbreviations because they:
• create confusion for international readers,
• are not intuitive for non-Latin-speakers,
• introduce ambiguity,
• complicate digital indexing and reference management.
Instead, they often require repeating shortened author–title information. Always check your target journal’s instructions before using “ibid.” or “id.”
7. Examples of Correct and Incorrect Usage
Correct:
1. Thompson, Social Behaviour, 122.
2. Ibid., 126.
1. García, Embodied Cognition, 45.
2. Ead., Neurophenomenology, 11.
Incorrect:
• using “ibid.” when an intervening citation appears,
• using “id.” when gender or authorship is uncertain,
• using “id.” to refer to a title (it refers only to a person),
• using either abbreviation when multiple sources appear in the previous note.
8. Should You Use These Abbreviations Today?
Use them only if:
• your discipline expects them,
• the journal or publisher explicitly permits them,
• your referencing style requires them,
• using them improves clarity rather than reducing it.
Otherwise, modern practice favours clarity through repetition.
9. Conclusion
“Ibid.” and the “id.” group remain important tools in certain fields, but they must be used with precision, caution and full understanding of their grammatical rules. When applied correctly, they streamline notes and prevent redundancy. When misused, they confuse readers, frustrate editors and introduce ambiguity into scholarly arguments.
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